The Future of Small Cell Deployments

MWC 2018 saw a strong emphasis on 4G and 5G densification using small cells, with many mobile service providers announcing plans to densify their networks. T-Mobile shared its 5G plan, stating that it would begin by deploying 5G upgradeable equipment and LTE-Advanced Pro technologies to ensure it had mobile 5G to offer in 30 markets in the United States when 5G smartphones become available next year. An important element of this strategy is the deployment of 25,000 LTE small cells using Licensed Assisted Access (LAA) technology, which is in the unlicensed bands. Also, Sprint specified that its 5G plan includes introducing 5G-ready equipment in 6 cities, which would include 40,000 outdoor small cells. Other global operators that stated continued activity in deploying small cells include Turkcell, Reliance Jio, and Telstra. In addition to mobile network operators, infrastructure providers, such as the tower company Crown Castle in the United States and Cellnex in Europe, have seen their small cell deployments continue and expect them to pick up the pace. Crown Castle stated it expects to deploy 25,000 small cells in 2018, in addition to the 50,000 it already operates.

On the small cell vendor front, there were also some announcements at MWC and even earlier in the year. CommScope’s small cell antenna announcement included support for Gigabit LTE with 4X4 MIMO and 2X2 MIMO in different bands. More broadly speaking, the vendor ecosystem has kept up a good pace of evolution. The most innovative product announcement was perhaps by Ubicquia, which introduced street light-powered small cells based on Qualcomm’s FSM architecture. Other examples include Philips lightingpartnering with American Tower to co-develop smart street lighting solutions that will also house 4G and eventually 5G small cells.

There has also been some interesting progress on the regulatory front in the United States. On March 22, 2018, the Federal Communications Commission (FCC) voted in favor of easing some federal requirements to lower the costs and time associated with gaining site approvals for the deployment of small cells. Similar considerations for reducing small cell deployment barriers have also been included for review in theEuropean 5G Action Plan.

Despite all the advancements and commitments, small cell deployments have been slow, as some of the key challenges remain. Even with the recent FCC reconsiderations regarding the small cell site acquisition process, there are still city and state requirements that vendors need to meet, which can differ dramatically across cities with a few proactively laying out plans to adopt small cells for 5G and smart city use cases.

One of the key challenges to small cell deployment is backhaul. This has been especially key as fiber-based backhaul seems to meet latency and capacity requirements better than microwave backhaul. While it is likely that an operator may choose to use both fiber and microwave, fiber has been the preferred choice. However, fiber buildout is a capital- and time-intensive endeavor, so for small cells to be a success for 5G, the first aspect to address would be the required support infrastructure.

This is also evident in the capital expenditure (CAPEX) guidance provided by the major carriers and network providers in the United States in 2017. During 4Q 2017, AT&T mentioned the important role of small cells in its 5G plan, but didn’t mention any CAPEX commitment for small cells. It did indicate, however, that fiber buildout would be a key focus area this year. Verizon also emphasized fiber buildout, along with 4G densification. Earlier in 2017, Verizon made headlines with its deal with Corning to purchase substantial fiber over a period of 3 years. T-Mobile, which purchases dark fiber capacity from its partners, stressed that it will build on its LTE capability and performance, with small cells being part of the approach. Sprint also mentioned densification as one of the drivers of its increase in CAPEX in 3Q 2017 and fiscal year (FY) 2017, expecting it to continue in FY 2018 with plans to deploy 40,000 outdoor small cell solutions. In January 2018, Sprint signed a partnership with Cox to use its wireline network for small cell backhaul.

Meanwhile, infrastructure providers have either made acquisitions or already have projects signed to deploy fiber. Uniti, for example, stated in January 28 that it has seven dark fiber projects and six major small cell projects, a large majority of which are scheduled for this year. Whether a mobile network operator chooses to deploy its own fiber or to contract with a partner, a strong backhaul network will be a key decision in determining the employability of small cells for 5G. Equally important is developing a reasonable expectation for the deployment time frame for both the backhaul network and small cell deployment, as it is not clear if any favorable regulatory changes will even reduce the overall deployment time dramatically.

5G hotspots based on small cells are expected to be the primary way of deploying 5G in the initial years. However, when operators state they are deploying small cells in LTE bands for densification as part of their 5G strategy, these deployments are currently in the sub-6 GHz bands. These small cells are upgradeable to 5G in similar bands in the sub-6 GHz range, but it is unlikely they will be upgradeable to mmWave bands without hardware changes. This implies that mmWave 5G networks will require new small cell hardware. This has strong implications for operators. Small cells are foundational to mmWave 5G, but in the sub-6 GHz range, operators could have the choice of deploying small cells on a market-by-market basis based on available spectrum and capacity requirements. This can be seen as an extension of network densification in Long-Term Evolution (LTE) networks, where small cells are crucial to meeting capacity requirements even in the Advanced Wireless Services (AWS) bands. It will most likely still be essential to deploy small cells, especially in dense urban areas. So, while 5G can be practically deployed in sub-6 GHz bands without small cells, it may still be core to an operator’s 5G strategy to ensure improved user experience.

To meet these requirements, commercially available small cells now span licensed, unlicensed, and shared spectrum. In terms of spectrum bands, products currently available support sub-1 GHz to 3.8 GHz frequency bands and 5 GHz in the unlicensed band. While all leading vendors are likely to add mmWave small cells to their portfolios, the mmWave small cell, combined with beamforming by Fujitsu in October 2017, provides a good idea of what we can expect. In addition to flexibility of spectrum bands, small cells also need to support advanced features that can enable operators to extend radio access network (RAN) automation features to the small cell network and also ease deployment and management of small cells.